Electromagnetic clutch



May 7, 1963 H. FISCHER ETAL ELECTROMAGNETIC CLUTCH Filed April 14. 1959 2 Sheets-Sheet 1 May 7, 1963 2 Sheets-Sheet 2 Filed April 14, 1959 ENTO United States Patent Ohce 3,088,567 Patented May 7, 1963 3,088,567 ELECTRMAGNETHC CLUTCH Hermann Fischer, Friedrichshafen-Fischbach, Hermann Straub, Friedrichshafen, Ludwig Wiedinann, Sharing, Friedrichshafen, Germany, and @tto heersen, Malvern, Pa., assignors to I-T-E Circuit Breaker Company, Phila-s delphia, Pa., a corporation of Pennsylvania File-tl Apr. 14, 1959, Ser. No. 806,355 Claims priority, application Germany Apr. 19, 19S 8 Claims. (Cl. 192-84) Our invention relates to an electromagnetic clutch of the stationary magnet type in which there is an axially directed air gap between the stationary magnet portion and the movable magnet portion having equal areas on either side of the air gap, and utilizes radiating tins on the stationary magnet portion for cooling purposes.

In the prior types of stationary magnet clutches, the magnetic structure includes a stationary portion and a movable portion which are magnetically connected through a rst and second air gap. These air gaps have previously been at least partially radially directed whereby an axial force is imposed upon the movable magnetic portion, thus necessitating radial bearing means.

In our invention, this problem is overcome through the use of axially directed air gaps instead of radially directed air gaps between the stationary magnet portion and the movable magnet portion.

In the axially directed air gap the gap on the larger diameter will have a larger cross-sectional area if the axial length of the air gap faces are the same. We have recognized this problem, and have over-come it by providing a U-shaped stationary magnet structure which contains a trapezoidally shaped energizing coil, and a cooperating trapezoidally shaped protrusion from the movable magnet structure extends into this opening. The two legs of the U-shaped stationary magnet lthus meet the protruding portion of the movable magnet structure along axially directed air gaps. Since, however, the protruding portion of the movable structure is trapezoidal in shape, the outer air gap will have a small axial length than will the inner air gap whereby the total crosssectional area of the two air gaps may be made identical so that the radial forces on the movable magnetic structure are exactly balanced. We have further found that the torque capacity of the clutch has been limited because of heat `generated within the energizing coil of the magnet body, and thus places a limit on the amount of heat that may be generated by the engaging clutch laminations. To increase the heat due to the energizing coil, and thus permit an increase in the heat generated by the laminations, we have found that the stationary magnet structure can be formed with a heat transfer means, such as radially directed tins which will both increase the external area of the stationary magnet structure and So increase its heat transfer ability, as well as permitting additional crosssectional area for the passage of magnetic flux.

As a second embodiment, we have found that a funnel means can be attached to the stationary magnet structure for clutches of the type which operate in an oil mist atmosphere whereby oil is condensed and collected in the funnels. These tunnels may then communicate with apertures which lead to the internal diameter of the clutch laminations whereby centrifugal force will ldrive the oil so conducted into the lamination area. Thus, the oil so collected will pass through the stationary magnet to effect some cooling thereof, and thereafter will reach the lamination area to continue to exert a cooling effect on the laminations.

Accordingly, a primary object of our invention is to provide a novel stationary magnet type of electromagnetic clutch wherein the effect of the -ux passing from the stationary magnet portion to a movable magnet portion exerts substantially no influence on the two parts.

Another object of our invention is to provide a novel electromagnetic clutch which yields high loa-d capacities for minimum dimensions.

A further object of our invention is to provide a novel manner for cooling electromagnetic clutches of the stationary magnet type.

Yet another object of our invention is to provide a novel electromagnetic clutch wherein a stationary magnet is magnetically connected to a movable magnet portion through an axially directed air gap.

A still further object of this invention is to .provide axially directed air gaps for connecting a stationary magnetic structure to a trapezoidally shaped movable magnetic structure whereby lthe axial length of the outer air gap is less than the axial length of `the inner air gap so that the total cross-sectional areas of the outer and inner air gaps are substantially lthe same.

These and other objects of our invention will become apparent from the following description when taken in connection with the drawings, in which:

FIGURE l shows a first embodiment of our invention wherein the movable magnetic structure of a stationary magnet clutch is trapezoidally shaped, and the stationary magnetic structure is provided with cooling fins.

FIGURE 2 is a side view of the clutch of FIGURE 1 when seen from the left-hand side, and particularly illustrates the radially directed cooling ns.

FIGURE 3 is a secon-d embodiment of our novel invention wherein the bushing carrying the inner lam-inations is externally positioned with respect to the inner portion of the rotatable magnet structure.

FIGURE 4 .is a still further embodiment of our invention, as shown in lFIGUR-E l, wherein a cooling medium for the clutch is a funnel device associated with a cooling plate and oil bore holes.

FIGURE 5 is a side view of FIGURE 4 when seen from the left-hand side.

FIGURE 6 is a cross-sectional view of FIGURE 4 when taken across the lines 6 6.

Referring now to the figures, we have illustrated our vinvention in connection with a generally well known type of stationary magnet clutch wherein a shaft is selectively connected to an output device, such as a gear, through a stack of interleaved laminations. For details of clutches utilizing this general construction, reference is made to copending application Serial No. 811,428, tiled May 6, 1959 and assigned to the assignee of the present invention.

In the embodiment of FIGURE l, a stationary magnet body 1 has a U-shaped cross-section which surrounds the magnet coil 2, and is supported with respect to shaft 3i, which may be the driving or driven member, by the needle bearing structure 4. Needle bearing structure 4 is described in detail in the above noted application, Serial No. 811,428.

The outer left-hand portion of magnet body 1 is provided with a plurality of cooling ribs 5, as shown in FIGURE 2, which are of the same magnetic material as is body 1, and may be formed integrally therewith. The cooling ribs 5 serve the dual function of increasing the external area of magnet body 1 so that it may be more effectively cooled by a cooling medium, and they further serve to conduct magnetic flux through body 1.

The movable portion of the magnetic structure for generating ilux through interleaved laminations of the clutch is generally shown as the trapezoidally shaped ring 6 which is magnetically connected to the stationary body 1 by the inner and outer axially directed air gaps 6a and 6b respectively. This trapezoidal cross-section is permissible because of the trapezoidal shape of coil 2, although it will be apparent to those skilled in the art that coil 2 may have the usual configuration of a rectangle, while the legs of the U-shaped magnet 1v may be of different lengths, so that when the movable magnet structure 6 encloses the opening of the stationary magnet it will, of necessity, have a trapezoidal shape.

Since the axially directed air gaps 6a and 6b which connect movable structure 6 and stationary structure 1 lie on different diameters, their total area would be different if the axial length of the gaps were the same. That is to say, the outer air gap which would have a greater diameter would have a greater total cross-sectional area than a smaller diameter air gap. However, by forming the movable magnetic portion 6 in a trapezoidal shape, we have made the axial length of the outer air gap smaller than the axial length of the inner air gap whereby the total cross-sectional area of the outer air gap is made the same as the total cross-sectional area of the inner air gap. In this way, it is apparent that a uniform magnetic flux is obtained, and there is no net axial force imposed on the movable magnetic structure 6, since all of the air gaps are axially directed.

In order to prevent short circuiting of the magnetic ux by ring 6, an intermediate annular insert 7 of nonmagnetic material is provided therein which has a conical cross-section having its larger base surface facing the magnet coil and its smaller base section facing the lami nation pack. More specifically, the clutch laminations of FIGURE 1 are shown as outer laminations 8 which cooperate with alternately positioned inner laminations 8a. Each of the laminations is provided with a nonmagnetic annular Zone 9' which may be an air gap or a non-magnetic insert, as described in copending applica tion Serial No. 811,428 tiled May 6, 1959, and assigned to the assignee of the present invention.

The smaller base portion of non-magnetic member '7 is immediately adjacent the position of the non-magnetic zones 9. The inner laminations of the lamination pack are supported by a cylindrical holder which is preferably of non-magnetic material in order to prevent leakage flux which by-passes the lamination pack.

In FIGURE l, the inner disk holder, or support mem- V ber 10, has a sleeve 11 forced thereon which is of nonmagnetic material. Sleeve 11 has a collar 12 integral therewith which is adjacent the face of the lower leg of magnet body 1 to prevent the axial passage of ux from the lower portion of magnet body 1.

Sleeve 11 is directly connected to shaft 3y so that it is rotated by shaft 3. Thus, the inner laminations 8a connectedto inner lamination support will be rotated with shaft 3.

The outer laminations, such as lamination 8, are connected to an outer disk support 14 which may subsequently be connected to a driving or driven member, such as a gear. The inner disk support 10 is directly fastened to movable magnetic portion 6 by means of radially disposed screws, such as screw 15.

In order to prevent leakage ux from the inner diameter of magnet body 1, its supporting needle bearings are provided with a cage of non-magnetic material, such as brass, while the needle bearings, structure 4 of FIGURE l, are shown as having an internal race which is directly connected to shaft 3. This race may be eliminated with the bearings 4 riding directly on a hardened outer surface of shaft 3.

Furthermore, the number of needle bearings in the cage may be reduced to as small a number as possible in order to keep the area for passage of flux as small as possible.

In operation, and assuming that shaft 3 is the driving member, as shaft 3 is rotated it will rotate lower disk support 10 and the inner laminations of the lamination pack and movable magnetic structure 6 which rotates with respect to stationary magnet 1. When coil 2 is energized it will generate a ilux, las shown by the dotted lines in FIGURE l, which circulates from the stationary magnetic body 1 through the axially directed air gaps to movable magnetic structure 6, through the interleaved lamination pack to Aan armature 9a, and thence back through the lamination pack magnet structure 6 and back to stationary magnet 1. Since `the armature 9a and the interleaved inner disks 8a are carri-ed by the non-magnetic support 1) to be rotatable therewith, but movable therewith in the usual manner, the armature 9a will move to the lett to compre-ss the stack of laminations against the right-hand surface of movable magnetic structure 6. Thus, the inner laminations will be connected to the outer larninations through the frictional engagement of the interleaved disks, and outer disk support 14 will, in effect, be directly connected to yshaft 3.

In a second embodiment of our invention, as shown in FIGURE 3, movable magnetic structure 16 corresponds to movable magnetic structure 6 of FIGURE 1. The movable struture 16 is directly connected to shaft 3 by means yof van extending collar or hub 17, and further provides 'a plurality of extending fingers, such as finger 16a, which serves as an outer disk support for the outer laminations ofthe lamination pack.

As was the case in FIGURE l, the movable magnetic structure L16 has a trapezoidally shaped cross-sectional area so :that the :total cross-sectional `area of the outer diameter axial air gap 18a is the same as the crossseotional area 'of the `lower diameter axial air gap r18b, 'and is provided with an insert i113 of non-magnetic material to prevent the .short circuiting of flux by the movable magnetic structure 16.

iIn the embodiment of FIGURE 3, the movable magnetic structure will simultaneously serve las a means for guiding the flux into Ithe lamination pack as well as a means for transmitting mechanical force. An inner lamination support 19 which carries the inner laminations in the usu-a-.l manner is an extending hub of an output drive member, Asuch as a gear. Thus, when the lamination pack is compressed, the driven member connected to hub 19 will be directly connected to shaft 3 through the movable magnetic structure 16. In order to prevent leakage flux, a plate 22 lof non-magnetic material is positioned between the lower portion of the movable magnetic structure y16 and the lower portion of the stationary magnet 1.

The opera-tion of the structure of FIGURE 3 is similar to that described for 'FIGURE 1 where flux generated in stationary magnet .1 will first traverse the outer diameter air gap 18a and then pass through the lamination stack to armature 9a, land thereafter return through the lamination pack to the lower portion of the movable magnetic lstructure 16, and thence through the inner axial gap 18b and back -to the stationary magnet '-1.

FIGURES 4, 5 and 6 show -a further embodiment of our novel invention in connection with a clutch of the general type shown in FIGURE l. In FIGURES 4, 5 and 6, however, we have replaced the .cooling ribs 5 of FIGURE 1 by a plate 26 which is directly fastened to the end surface of stationary magnet 1. Cooling plate 26, which is stationary, carries an upright funnel 27 which communicates with bores A28 and 29 in magnet body 1. Bore 29 extends through the magnet `body and terminates 1n openings 30 in ring 10. Openings 30 then communicate with the lamination pack formed by the inner and outer laminations through the radial openings 32, as best seen in FIGURES 4 and 6.

In operation, if the clutch is contained within an enclosed housing with an oil mist used for lubrication, it will be apparent that oil will condense on cooling plate 26 Iand flow downwardly into funnel 27. From funnel 27 the condensed oil will pass through bores 28 and 29 and into openings 30 in the inner `disk support 10. Since the inner disk support .10 rotates, the oil will be forced outwardly and through radial bores 32 toward the clutch disks. In this manner, the frictional heat produced from the clutch disks is transferred to the oil which is subsequenstly thrown ont ofthe lamination pack. In the event that Ithere is no oifl for the operation, the funnel 27 may be supplied with oil through an adjacently positioned pipe, such as pipe 33.

Although We have described preferred embodiments of our novel invention, many variations and modifications will now be obvious to those skilled in the tant, and we prefer ltherefore to be Limited not by the specific disclosure herein but only by the appended claims.

We claim:

l. In an electromagnetic clutch; a stationary magnetic structure and a movable magnetic structure; said Stationary magnetic structure having an annular opening therein; said annular opening receiving a coil at the bottom thereof; said movable magnetic structure including a ring shaped member; at least a portion of said ring shaped member being movably positioned within said annular opening of said stationary magnetic structure and being rotable with respect to said stationary magnetic structure; said movable magnetic structure being magnetically connected to said stationary magnetic structure by air gaps along the inner and outer diameter of said annular shaped opening in said stationary magnetic s-tructure; said portion of said ring shaped member positioned within said annular opening having a trapezoidal shape whereby the total area of said air gaps etective to transmit force to said movable magnetic structure on said inner and outer diameters of said annular opening are substantially equal.

2. In an electromagnetic clutch: a stationary magnetic structure and a movable magnetic structure; said stationary magnetic structure having an annular opening therein; said annular opening receiving a coil at the bottom thereof; said movable magnetic structure including a ring shaped member; at least a portion of said ring shaped member being movably positioned within said annular opening of said stationary magnetic structure and being rotatable with respect to said stationary magnetic structure; said movable magnetic structure being magnetically connected to said stationary magnetic structure by air gaps along the inner and outer diameter of said annular shaped opening in said stationary magnetic structure; said portion of said ring shaped member positioned Within said annular opening having a trapezoidal shape whereby the total area of said air gaps on said inner and outer diameters of said annular opening are substantially equal; said coil having a trapezoidal shape cooperating with said trapezoidal shape of said portion of said ring shaped member.

3. In an electromagnetic clutch; a stationary magnetic struc-ture and a movable magnetic structure; said stationary magnetic structure having an annular opening therein; said annular opening receiving a coil at the bottom thereof; said movable magnetic structure including a ring shaped member; at least a portion of said ring shaped member being movably positioned Within said annular opening of said stationary magnetic structure and being rotatable with respect to said stationary magnetic structure; the surface of said stationary magnetic struc- `ture opposite the surface having said annular opening therein having radial tins; said radial tins being integral with said stationary magnetic structure and being operative to increase the external area of said stationary magnetic structure and to conduct flux generated by said coil.

4. In an electromagnetic clutch; a stationary magnetic structure and a movable magnetic structure; said stationary magnetic structure having an annular opening therein; said annular opening receiving a coil at the bottom thereof; said movable magnetic structure including a ring shaped member; at leas-t a portion of said ring shaped member being movably positioned within said annular opening of said stationary magnetic structure and being rotatable with respect to said stationary magnetic structure; said movable magnetic structure being magnetically connected to said stationary magnetic structure by air gaps along the inner and outer diameter of said annular shaped opening in said stationary magnetic structure; said portion of said ring shaped member positioned Within said annular opening having a trapezoidal shape whereby the total area 4of said air gaps on said inner and outer diameters of said annular opening are substantally equal; said coil having a trapezoidal shape cooperating with said trapezoidal shape of said portion of said ring shaped member; the surface of said stationary magnetic structure opposite the surface having said annular opening therein having radial tins; said radial ns being integral with said stationary magnetic structure and being 'operative to increase the external area of said stationary magnetic structure and to conduct ilux generated by said coil.

5. A stationary magnetic structure for an electromagnetic clutch; one external surface of said stationary magnetic structure having radial iin means extending therefrom; said radial n means being integral with said stationary magnetic structure and being operative to contribute to the cross-sectional linx carrying area of said stationary magnetic structure and to increase the external surface area of said stationary magnetic structure.

6. An electromagnetic clutch; said electromagnetic clutch comprising a driving member and a :driven member; said driving member being `operatively co-nnected to a lirst plurality of laminations; said driven member being operatively connected to a second plurality of laminations; the laminations of said lfirst and second plurality ott laminations being interleaved; a magnetic structure for generating a magnetic iiux through said rst and second pluralities of laminations for compressin-g said laminations; 4said magnetic structure including a relatively stationary magnetic structure and a relatively movable magnetic structure; one of said driving or driven members being operatively connected to said relatively movable magnetic structure; said stationary magnetic structure having an annular opening therein; said annular opening receiving -a coil `at the bottom thereof; said movable magnetic structure including a ring shaped member; at least a portion of said ring shaped member being movably positioned With-in said annular opening of said stationary magnetic structure; said movable magnetic structure being magnetically connected to said stationa-ry magnetic structure by air gaps along the inner and Aouter diameter of said annular shaped opening in said stationary magnetic structure; said portion of said ring shaped member positioned within said annular opening having a trapezoidal shape whereby the total area of said a-ir gaps on said inner and outer .diameters of said annular opening are substantially equal; said coil having a trapezoidal shape cooperating with said trapezoidal shape of said portion of said ring shaped member.

7. An electromagnetic clutch; said electromagnetic clutch `comprising a driving member and a driven member; said driving member being operatively connected to a rst plurality of laminations; said driven member being `operatively connected to a second plurality of laminations; the laminations of said iirst and second plurality of laminations .being interleaved; a magnetic structure for Igenerating a magnetic flux through said iirst and second pluralities of laminations for compressing said laminations; lsaid magnetic structure including a relatively stationary magnetic structure yand a relatively movable magnetic structure; said driving member being operatively connected to said relatively movable magnetic structure; said stationary magnetic structure having an annular opening therein; said annular opening receiving a coil at the bottom thereof; said movable magnetic structure including a ring shaped member; at least a portion of said ring shaped member being movably positioned within said annular opening of said stationary magnetic structure; said movable magnetic structure being magnetically connected to said stationary magnetic structure by air gaps valong the inner and outer diameter of said annular shaped opening in said stationary magnetic structure; the surface of said stationary magnetic structure opposite the surface having said .annular opening therein having radial ins; said radial ns being integral with said stationary magnetic structure and being operative to increase the external area of said stationary magnetic structure and to conduct flux generated by said coil.

8. An electromagnetic clutch; said electromagnetic clutch comprising a driving member and a driven member; said driving member being operatively connected to a rst .plurality of laminations; said driven member being operatively connected .to a second plurality of laminations; the laminations of -said rst and second plurality of laminations being interleaved; a magnetic structure for .generating a magnetic ux through said iirst and second pluralities of laminat-ions for compressing said laminations; said magnetic structure including a relatively stationary magnetic structure and a relatively movable magnetic structure; said driving member being operatively connected to said relatively movable magnetic structure; one external sunface of said stationary magnetic structure having radial `iin means extending therefrom; said radial fin means being integral with said stationary magnetic structure' and being operative to contribute to the cross-sectional `flux carrying area of said stationary magnetic structure and to increase the external surface area of said stationary magnetic structure.

References Cited in the le of this patent UNITED STATES PATENTS 2,115,763 Burke May 3, 1938 2,512,065v Du Rostu June 20, 1950 2,549,217 Mason Apr. 17, 1951 2,729,318 Harter Jan. 3, 1956 2,785,781 Johansen Mar. 19, 1957 2,857,998 Harter Oct. 28, 1958 2,861,664 Simon et al Nov. 25, 1958 2,936,053 Reucker May 10, 1960.

FOREIGN PATENTS 37,268 Switzerland June 9, 1906 

1. IN AN ELECTROMAGNETIC CLUTCH; A STATIONARY MAGNETIC STRUCTURE AND A MOVABLE MAGNETIC STRUCTURE; SAID STATIONARY MAGNETIC STRUCTURE HAVING AN ANNULAR OPENING THEREIN; SAID ANNULAR OPENING RECEIVING A COIL AT THE BOTTOM THEREOF; SAID MOVABLE MAGNETIC STRUCTURE INCLUDING A RING SHAPED MEMBER; AT LEAST A PORTION OF SAID RING SHAPED MEMBER BEING MOVABLY POSITIONED WITHIN SAID ANNULAR OPENING OF SAID STATIONARY MAGNETIC STRUCTURE AND BEING ROTABLE WITH RESPECT TO SAID STATIONARY MAGNETIC STUCTURE; SAID MOVABLE MAGNETIC STRUCTURE BEING MAGNETICALLY CONNECTED TO SAID STATIONARY MAGNETIC STRUCTURE BY AIR GAPS ALONG THE INNER AND OUTER DIAMETER OF SAID ANNULAR SHAPED OPENING IN SAID STATIONARY MAGNETIC STRUCTURE; SAID PORTION OF SAID RING SHAPED MEMBER POSITIONED WITHIN SAID ANNULAR OPENING HAVING A TRAPEZOIDAL SHAPE WHEREBY THE TOTAL AREA OF SAID AIR GAPS EFFECTIVE TO TRANSMIT FORCE TO SAID MOVABLE MAGNETIC STRUCTURE ON SAID INNER AND OUTER DIAMETERS OF SAID ANNULAR OPENING ARE SUBSTANTIALLY EQUAL. 